1. Field of the Invention
The present invention relates to a rotary drive which serves to turn or swivel two structural parts relative to each other. More specifically, the present invention relates to a rotary drive with a drive element, which serves to turn or swivel two structural parts relative to each other. The drive has an outer tube and at least one end piece that is able to rotate in relation to the outer tube without shifting axially.
2. Description of the Related Art
The related art involves rotary drives which serve to turn or swivel two structural parts relative to each other. Such structural parts can be doors, covers or the like of furniture or vehicles. Likewise, such rotary drives can be used to swivel furniture parts relative to each other, e.g., head or foot parts of bedsteads relative to the bed frame.
In DE 103 21 807 A1, FIGS. 1 and 2, a rotary drive of this kind is shown. In an outer tube is arranged a helical slider, able to move axially but not able to rotate, being moved in the outer tube from an electric motor by means of a threaded spindle. Arranged axially parallel to the threaded spindle is a helical shaft with a steep thread, which meshes with a thread profile of the helical slider. The helical shaft is led out axially from the outer tube at both ends. If the helical slider is shoved axially in the outer tube, the helical shaft will turn, as is known, e.g., for screw drills. The helical shaft led out from the outer tube at both ends is thus rotated relative to the outer tube. The pitch of the nonbraking steep thread of the helical shaft is a multiple of the pitch of the threaded spindle, so that a strong speed reduction or torque transmission results between the drive motor and the rotary drive. The drawback here is that the drive motor is arranged outside the outer tube and makes a bend relative to this. Furthermore, the axially parallel arrangement of the threaded spindle and the helical shaft results in a relatively large overall diameter of the rotary drive.
Moreover, in DE 103 21 807 A1, FIGS. 6 and 7, a rotary drive is shown wherein the threaded spindle, driven by the outer drive motor arranged at a bend, is coaxially arranged in the outer tube. A helical slider runs on the threaded spindle, being led without rotation by additional linear guides, which are arranged axially parallel to the threaded spindle in the outer tube. The outer tube sits on the helical slider with a steep threading, so that the axial displacement of the helical slider leads to a rotation of the outer tube. Besides the drive motor once again being arranged at a bend outside the outer tube, one drawback of this configuration is that the outer tube has helical grooves, so that the outer tube cannot be manufactured in simple fashion in an extrusion or drawing process. The linear guides arranged axially parallel in the outer tube moreover enlarge the diameter of the rotary drive.
What is not appreciated by the prior art is that an axially parallel arrangement of the threaded spindle and the helical shaft in rotary drives results in a relatively large overall diameter of the rotary drive. Additionally, in those configurations utilizing helical grooves, the outer tube cannot be manufactured in a simple fashion by an extrusion or drawing process. The linear guides arranged axially parallel in the outer tube moreover enlarge the diameter of the rotary drive.
Accordingly, there is a need for an improved rotary drive so that more compact outer dimensions can be realized and the manufacturing of the rotary drive can be simplified.